Field of the Invention
The present invention relates to an organic light emitting display panel and a method of manufacturing the same, and more particularly, to a flexible organic light emitting display panel and a method of manufacturing the same.
Discussion of the Related Art
Display devices such as LCD (Liquid Crystal Display) devices, OLED (Organic Light Emitting Diode) devices, PDP (Plasma Display Panel) devices, and EPD (Electrophoretic Display) devices are manufactured through several steps including an imprinting process to form a pattern on a substrate.
Flat panel display (FPD) apparatuses are applied to various electronic devices such as portable phones, tablet personal computers (PCs), notebook computers, etc. Examples of FPD apparatuses include LCD apparatuses, PDP apparatuses, OLED apparatuses, etc.
Of these FPD apparatuses, OLED apparatuses are a self-emitting device, and thus, have a fast response time, high emission efficiency, high luminance, and a broad viewing angle. As a result, OLED apparatuses are attracting much attention as next-generation FPD apparatuses.
A flexible OLED apparatus including a flexible organic light emitting (OLE) display panel has been developed recently.
FIG. 1 is a cross-sectional view illustrating a top-emission type flexible OLE display panel according to the related art. FIG. 2 is a plan view illustrating a flexible OLE display panel equipped with a substrate according to the related art.
Flexible OLE display panels may be categorized into a bottom emission type, which outputs light in a lower-end direction as illustrated in FIG. 1, and a top emission type which outputs light in an upper-end direction.
The top emission type flexible OLE display panel, as illustrated in FIG. 1, includes an upper substrate 20, which includes a color filter 21, an upper base substrate (a transparent polyimide (PI)) 22, and a front film 23, and a lower substrate 10 which includes a multi-buffer 13, a thin film transistor (TFT) 14, an organic light emitting diode (OLED) 15, and a sealing material 16. Here, the front film 23 may perform a function of protecting the upper substrate 20.
As illustrated in FIG. 2, the upper substrate 20 is bonded to an active area of the lower substrate 10, and a pad area of the lower substrate 10 is opened for connecting a chip-on film (COF) 40, connected to a printed circuit board (PCB) 50, to a pad 18 included in the lower substrate 10.
The bottom emission type flexible OLE display panel may not need an upper substrate. For example, in the bottom emission type flexible OLE display panel, a color filter and an OLED are stacked on a base substrate, and then, the OLED is sealed by a sealing material. In this case, a reflector is bonded to an upper end surface of the bottom emission type flexible OLE display panel.
The flexible OLE display panel according to the related art may have the following problems.
First, in a glass-type, large-area OLED display, in order to prevent water from penetrating through a side, a thickness of a resin 30 coated on a pad area is desired to be about 400 μm. However, since a thickness of a flexible OLE display panel is thin, a thickness of the resin 30 coated on the pad area of the flexible OLE display panel is typically equal to or less than 70 μm. As a result, it may be difficult to prevent water from penetrating through a side of the flexible OLE display panel.
If a thickness of the flexible OLE display panel is increased for preventing penetration of water, the flexible characteristics of the OLE display panel may be compromised. The resin 30, as illustrated in FIG. 1, may protect a bonding part to which the COF 40 is attached.
Second, due to thermal expansion and contraction characteristics of transparent polyimide (PI) and a stress difference of an inorganic layer which is formed through a high temperature deposition process in a TFT process, when the flexible OLE display panel is released from the base substrate, the pad area may roll up.
Third, due to the resin coated on the pad area for preventing penetration of water, the flexible OLE display panel may cling to a chuck during a release and back film lamination process.
Fourth, a film may be attached to an upper end surface of the flexible OLE display panel for preventing water from penetrating through a side. However, due to the resin coated on the pad area, the film may not be completely attached to the side of the flexible OLE display panel. Moreover, when the resin is covered by the film, bubbles may occur in the resin.
Fifth, several to several tens of COFs equipped with a source driver integrated circuit (IC) are attached to the pad area for connecting the source driver IC to the flexible OLE display panel. A process of aligning an electrode pad provided on each of the COFs and an electrode pad provided in the pad area is typically needed. For example, as illustrated in FIG. 2, when twelve COFs 140 are attached to the flexible OLE display panel, twelve alignment processes may be needed. Moreover, an alignment process of attaching the twelve COFs 140 to the PCB 50 may be needed, which also may require an alignment margin between the electrode pads.
Sixth, in the bottom emission type flexible OLE display panel, a process of attaching a reflector (for example, a face seal metal (FSM) or a metal sheet)) to the upper end surface of the flexible OLE display panel may be needed. As a result, the manufacturing process may become complicated, and the manufacturing cost may increase.
Seventh, in the bottom emission type flexible OLE display panel, as illustrated in FIG. 2, the upper substrate 20 is bonded to the active area of the lower substrate 10. As a result, a process of aligning the upper substrate 20 to the active area of the lower substrate 10 may be needed.